Severe delayed-onset hypersensitivity reactions to amoxicillin in children

Area of Science:

• Pediatric Allergy and Immunology
• Pharmacology
• Infectious Diseases

Background:

• Amoxicillin is a widely prescribed aminopenicillin for respiratory and ear infections.
• Serious adverse reactions to amoxicillin are generally infrequent.
• Hypersensitivity reactions can occur, but their specific mechanisms and triggers in children warrant further investigation.

Purpose of the Study:

• To investigate the cause of delayed-onset hypersensitivity reactions in children treated with amoxicillin.
• To evaluate the role of amoxicillin versus excipients in these reactions.
• To correlate clinical presentation with immunologic testing results.

Main Methods:

• Retrospective case series of 11 children (6 months to 10 years) presenting with delayed hypersensitivity reactions.
• Clinical symptoms documented, including urticaria, angioedema, arthritis, and arthralgia (serum-sickness-like illness).
• Immunologic testing performed, including Radioallergosorbent testing (RAST) for IgE antibodies and lymphocyte transformation testing (LTT).

Main Results:

• 10 out of 11 children experienced serum-sickness-like reactions.
• RAST for IgE antibodies to penicillin was negative in all tested children.
• LTT was positive in only one patient, suggesting limited IgE-mediated or T-cell mediated hypersensitivity to amoxicillin.
• Reactions occurred exclusively in children receiving an amoxicillin solution.

Conclusions:

• The negative immunologic test results and the specific presentation in children receiving amoxicillin solution suggest that excipients may be responsible for these delayed hypersensitivity reactions.
• Further research is needed to identify specific excipients causing these reactions and to develop safer formulations.
• This finding has implications for pediatric prescribing practices and adverse event monitoring of amoxicillin formulations.